Using reclaimed stone instead of concrete can offer environmental, as well as
aesthetic, benefits.

The Norman church of Saint Peter in the Cotswold village of Farmington is a tiny gothic gem guarding one thousand years of parish history. Its walls, archways and pillars are all from the local stone: a luscious buttery yellow limestone that comes out of the earth soft enough to carve fine detail with a chisel, and which hardens to become a long-lived building material. Farmington stone is part of the seam of Oolitic Cotswold limestone that makes the built environment of much of Oxfordshire and Gloucestershire such a glorious mellow blend of cream, gold and yellow.

For decades abandoned by architects in love with cheaper concrete's modernist possibilities, stone is now increasingly being chosen for steps, floors, walls and decorative features by home owners and builders concerned both for aesthetics and sustainability. While concrete 'rots' and crumbles, sometimes after only a few years, evidence for stone's longevity is all around us, from the fine twelfth century chevron- carved chancel arch in Farmington church to the Elgin marbles. Stone lasts – and it gets more, not less, beautiful with time.

Concrete, made from cement, sand and aggregates has high 'embodied energy' compared to stone, mainly because of the cement content. Embodied energy is the amount of carbon dioxide produced during a building material's extraction, manufacture and distribution.

Cement, which requires limestone and clays to be fired at high temperatures, has high embodied energy. Materials with low embodied energy include reclaimed bricks, flagstones and recycled tiles. New stone can have low embodied energy although this depends on its hardness, extraction methods and where it is quarried. Hard Chinese granite, for example, quarried on a vast industrial, wasteful scale with explosives, has high embodied energy. Farmington stone, soft enough to be 'plucked' by diggers out of the ground and carved by hand to produce very little waste, has relatively low embodied energy. According to Bath University's guide to the embodied energy of construction materials, concrete rates an average of 0.130 kg of carbon dioxide per kg and pre- fabricated concrete about double that. New limestone has 0.017 kg of carbon dioxide perkg and slate between 0.006 – 0.06. Marble, a harder stone has higher embodied energy of 0.112, although this is still lower than concrete.

A more comprehensive rating system, measuring not just carbon dioxide but water use, toxicity and waste is the Building Research Establishment's Green Guide, a comprehensive list of construction materials, rating them A+ to E. The Guide for example rates reclaimed British slate as A+, Italian imported marble as C and imported Chinese granite setts as E.

Builder Matt Harding has recently completed a new regency-style home in Cheam, Surrey. One of the most impressive architectural features of the house is its soaring two storey limestone staircase weighing nearly five tonnes and made with solid stone rather than concrete with limestone cladding, saving around 1,000 kg of carbon dioxide from the construction process. While Matt says his decision to go for solid stone rather than concrete or steel was mainly aesthetic, he took environmental considerations into account too. "That staircase will outlive the house," he says. The decision cost him £20,000 however as the solid stone staircase cost £80,000 as opposed to the £60,000 a concrete and cladding one would have cost. While Matt Harding's house – sold recently for £3.85 million - may be an extreme example of choosing stone as an environmental choice, if you're planning a new kitchen floor, patio steps or fireplace this year then consider stone – preferably reclaimed - rather than concrete as a beautiful alternative.

"Old Cotswold building stones, or York flagstones can be cleaned up and used again and again and again, says Liza Hanks, who owns Cotswold-based Winchcombe Reclamation. "We employ seven people who chip off old lime mortar, re-dress and if necessary re- drill old stone tiles, bricks, fireplaces, copings and quoins. My big plea to people re-using these materials - that may well have been recycled several times over centuries - is to use lime, rather than cement mortar as hard cement mortar is impossible to remove from old stones."

She says before buying new stone, people should visit the quarry producing it, and ask to see the terms of its extraction license so they can judge for themselves the extraction and processing methods, which vary widely between quarries.

Next Sunday (April 27) The Low Carbon Trust is holding a Green Architecture Day in Brighton. Among inspirational projects are the 'House Made from Waste' featuring recycled materials with very low or no embodied energy including latex gloves, old cd cases and the stuffing from old duvets. For more information visitbrightonpermaculture.org.uk